Watch This Space
It was quite a surprise to discover, when I looked it up, that the most
famous experiment we carried out while we were on the moon had its
begimungs way back in 19SS. At that time, high-altitude rocket
research had been going for only about ten years, mostly at White
Sands, New Mexico. Nineteen fifty-five was the date of one of the most
spectacular of those early experiments, one that involved the ejection
of sodium into the upper atmosphere.
On Earth, even on the clearest night, the sky between the stars isn't
completely dark. There's a very faint background glow, and part of it
is caused by the fluorescence of sodium atoms a hundred miles up. Since
it would take the sodium in a good many cubic miles of the upper
atmosphere to fill a single matchbox, it seemed to the early
investigators that they could make quite a fireworks display if they
used a rocket to dump a few pounds of the stuff into the ionosphere.
They were right. The sodium squirted out of a rocket above White Sands
early in 195S produced a great yellow glow in the sky which was
visible, like a kind of artificial moonlight, for over an hour, before
the atoms dispersed. This experiment wasn't done for fun (though it
was fun) but for a serious scientific purpose. Instruments trained on
this glow were able to gather new knowledge about the upper air
knowledge that went into the stockpile of information without which
space flight would never have been possible.
When they got to the moon, the Americans decided that it would be a
good idea to repeat the experiment there, on a much larger scale. A
few hundred kilograms of sodium fired up from the surface would produce
a display that would be visible from Earth, with a good pair of field
glasses, as it fluoresced its way up through the lunar atmosphere.
(Some people, by the way, still don't realize that the moon has an
atmosphere. It's about a million times too thin to be breathable, but
if you have the right instruments you can detect it. As a meteor
shield, it's first-rate, for though it may be tenuous it's hundreds of
miles deep.)
Everyone had been talking about the experiment for days. The sodium
bomb had arrived from Earth in the last supply rocket, and a-very
impressive piece of equipment it looked. Its operation was extremely
simple; when ignited, an incendiary charge vaporised the sodium until a
high pressure was built up, then a diaphragm burst and the stuff was
squirted up into the sky through a specially shaped nozzle. It would
be shot off soon after nightfall, and when the cloud of sodium rose out
of the moon's shadow into direct sunlight it would start to glow with
tremendous brilliance.
Nightfall, on the moon, is one of the most awe-inspiring sights in the
whole of nature, made doubly so because as you watch the sun's flaming
disk creep so slowly below the mountains you know that it will be
fourteen days before you see it again. But it does not bring darkness
at least, not on this side of the moon. There is always the Earth,
hanging motionless in the sky, the one heavenly body that neither rises
nor sets. The light pouring back from her clouds and seas floods the
lunar landscape with a soft, blue-green radiance, so that it is often
easier to find your way around at night than under the fierce glare of
the sun.
Even those who were not supposed to be on duty had come out to watch
the experiment. The sodium bomb had been placed at the middle of the
big triangle formed by the three ships, and stood upright with its
nozzles pointing at the stars. Dr.
Anderson, the astronomer of the American team, was testing the firing
circuits, but everyone else was at a respectful distance. The bomb
looked perfectly capable of living up to its name, though it was really
about as dangerous as a soda-water siphon.
All the optical equipment of the three expeditions seemed to have been
gathered together to record the performance. Telescopes,
spectroscopes, motion-picture cameras, and everything else one could
think of were lined up ready for action. And this, I knew, was nothing
compared with the battery that must be zeroed on us from Earth. Every
amateur astronomer who could see the moon tonight would be standing by
in his back garden, listening to the radio commentary that told him of
the progress of the experiment. I glanced up at the gleaming planet
that dominated the sky above me; the land areas seemed to be fairly
free from cloud, so the folks at home should have a good view. That
seemed only fair; after all, they were footing the bill.
There were still fifteen minutes to go. Not for the first time, I
wished there was a reliable way of smoking a cigarette inside a space
suit without getting the helmet so badly fogged that you couldn't see.
Our scientists had solved so many much more difficult problems; it
seemed a pity that they couldn't do something about that one.
To pass the time for this was an experiment where I had nothing to do I
switched on my suit radio and listened to Dave Bolton, who was making a
very good job of the commentary. Dave was our chief navigator, and a
brilliant mathematician. He also had a glib tongue and a picturesque
turn of speech, and sometimes his recordings had to be censored by
the
BBC.
There was nothing they could do about this one, however, for it was
going out live from the relay stations on Earth.
Dave had finished a brief and lucid explanation of the purpose of the
experiment, describing how the cloud of glowing sodium would enable us
to analyze the lunar atmosphere as it rose through it at approximately
a thousand miles an hour.
"However," he went on to tell the waiting millions on Earth, "let's
make one point clear. Even when the bomb has gone off, you won't see a
darn thing for ten minutes and neither will we. The sodium cloud will
be completely invisible while it's rising up through the darkness of
the moon's shadow.
Then, quite suddenly, it will flash into brilliance as it enters the
sun's rays, which are streaming past over our heads right now as we
stare up into space. No one is guise sure how bright it will be, but
it's a pretty safe guess that you'll be able to see it in any telescope
bigger than a two-inch. So it should just be within the range of a
good pair of binoculars."
He had to keep this sort of thing up for another ten minutes, and it
was a marvel to me how he managed to do it. Then the great moment
came, and Anderson closed the firing circuit. The bomb started to
cook, building up pressure inside as the sodium volatilised. After
thirty seconds, there was a sudden puff of smoke from the long, slender
nozzle pointing up at the sky. And then we had to wait for another ten
minutes while the invisible cloud rose to the stars. After all this
build-up, I told myself, the result had better be good.
The seconds and minutes ebbed away. Then a sudden yellow glow began to
spread across the sky, like a vast and unwavering aurora that became
brighter even as we watched. It was as if an artist was sprawling
strokes across the stars with a flame-filled brush. And as I stared at
those strokes, I suddenly realised that someone had brought off the
greatest advertising coup in history. For the strokes formed letters,
and the letters formed two words the name of a certain soft drink too
well known to need any further publicity from me.
How had it been done? The first answer was obvious. Someone had
placed a suitably cut stencil in the nozzle of the sodium bomb, so that
the stream of escaping vapor had shaped itself to the words. Since
there was nothing to distort it, the pattern had kept its shape during
its invisible ascent to the stars. I had seen skywriting on Earth, but
this was something on a far larger scale.
Whatever I thought of them, I couldn't help admiring the ingenuity of
the men who had perpetrated the scheme. The O's and A's had given them
a bit of trouble, but the C's and L's were perfect.
After the initial shock, I am glad to say that the scientific program
proceeded as planned. I wish I could remember how Dave Bolton rose to
the occasion in his commentary; it must have been a strain even for his
quick wits. By this time, of course, half the Earth could see what he
was describing. The next morning, every newspaper on the planet
carried that famous photo of the crescent moon with the luminous slogan
painted across its darkened sector.
The letters were visible, before they finally dispersed into space, for
over an hour. By that time the words were almost a thousand miles
long, and were beginning to get blurred. But they were still readable
until they at last faded from sight in the ultimate vacuum between the
planets.
Then the real fireworks began. Commander Vandenburg was absolutely
furious, and promptly started to grill all his men. However, it was
soon clear that the saboteur if you could call him that had been back
on Earth. The bomb had been prepared there and shipped ready for
immediate use. It did not take long to find, and fire, the engineer
who had carried out the substitution. He couldn't have cared less,
since his financial needs had been taken care of for a good many years
to come.
As for the experiment itself, it was completely successful from the
scientific point of view; all the recording instruments worked
perfectly as they analyzed the light from the unexpectedly shaped
cloud. But we never let the Americans live it down, and I am afraid
poor Captain Vandenburg was the one who suffered most. Before he came
to the moon he was a confirmed teetotaler, and much of his refreshment
came from a certain wasp-wasted bottle. But now, as a matter of
principle, he can only drink beer and he hates the stuff.